This invention relates to a synchronizer having self-energizing and means to limit force provided by the self-energizing means.
Synchronizers for use in multi-ratio transmissions are well known. Such synchronizers include pairs of friction and jaw members for respectively synchronizing and positively clutching a gear to a shaft, pre-energizer assemblies for engaging the friction members in response to initial engaging movement of a shift sleeve, a hub rotatably fixed to the shaft and having external spline teeth slidably receiving internal spline teeth of the shift sleeve which often defines one of the jaw member pairs, a baulkring having blocker teeth for arresting engaging movement of the shift sleeve until synchronization is reached and for transferring a shift force from the sleeve to increase the engaging force of the friction members.
It is also known that such synchronizers may be used to reduce shift time and shift effort required by a vehicle operator by providing the synchronizers with self-energizing means and that springs may be used to limit forces provided by the self-energizing means. U.S. Pat. No. 5,678,670 discloses a synchronizer having all of the above features and U.S. Pat. No. 5,544,727 discloses all but the spring regulating feature.
An object of this invention is to provide a synchronizer with self-energizing and improved force limiting of the self-energizing.
The invention relates to a synchronizer frictionally synchronizes and positively connects first and second drives disposed for relative rotation about a common axis, and the synchronizer comprises: A first element affixed against rotation and axial movement relative to the first drive and has an annular periphery with external splines. A second element includes an annular periphery with internal splines defining first jaw means and axially movable from a neutral position to an engaged position with second jaw means for positively connecting the drives in response to engaging movement of the second element by an axially directed first shift force (Fo). The second element includes internal splines mating continuously with the external splines in close slidable relation for preventing relative rotation therebetween between. A first ring includes a first friction surface axially movable into engagement with a second friction surface in response to the engaging movement of the second element for producing a synchronizing torque (To). First and second pluralities of blocker surfaces are movable into engagement in response to the engaging movement of the second element for preventing asynchronous engagement of the jaw means and for transmitting the first shift force (Fo) to the first friction surface to effect an engagement force of the friction surfaces. The second plurality of blocker surfaces are affixed to the first ring. Pluralities of first and second self-energizing means respectively include first and second ramps operative when engaged to react the synchronizing torque for producing an additive axial force (Fa) in the direction of the first shift force (Fo) and for increasing the engagement force of the friction surfaces. One of the first and second self-energizing means includes means for directing the additive axial force (Fa) to the first friction surface via the blocker surfaces. Each of the first self-energizing means are mounted on one of the elements and each of the second self-energizing means are mounted for non-radial movement and limited rotation relative to another of the elements.
The improvement is characterized by resilient means for limiting the additive axial force to a predetermined amount. Each of the first self-energizing means including a member movably mounted on the one of the elements and defining one of the first self-energizing ramps. The member is movable against the resilient means in response to the additive axial force (Fa) exceeding the predetermined amount.